Yahoo!, Microsoft and Google have come under fire for their China activities in a new report from Amnesty International.

Amnesty says the three companies have "violated their stated corporate values and policies in pursuit of the potentially lucrative Chinese market."

"The Internet should promote free speech, not restrict it. We have to guard against the creation of two Internets — one for expression and one for repression," said Larry Cox, executive director of Amnesty International USA (AIUSA). "It's up to citizens worldwide to keep governments and corporations accountable."

In China, Amnesty says Yahoo! has handed over private information that led to the imprisonment of two journalists, Shi Tao and Li Zhi. The company has also voluntarily signed China's "Public Pledge on Self-discipline for the Chinese Internet Industry," agreeing to censor and deny access to information.

The organization also says Microsoft shut down the blog of New York Times researcher Zhao Jing at the government's request while Google has launched a censored version of its international search engine.

Amnesty calls on these three companies to be transparent about their dealings with the Chinese authorities, revealing details of agreements and Web filtering arrangements.